Best way to attach metal legs to corner desk? Do I need extra support?

Question

I'm making my own office desk, I'm 2m04cm so the height and depth are appropriate.

I've made the desk top from reclaimed floorboards. It's 1 inch thick, the supports underneath are from the same source. It's 19 inch (49cm) wide and 56x75 (142x190cm) in length.

I've had these legs custom made to the height I need. The top plate has 6 counter sunk holes in. The top and bottom plate are 17.5 inches long, 3 inches wide (7x47cm).

I also have a corner leg.

What I need help with is based on the size of the desk top and legs what's the best way of attaching the legs to the desk top.

Should I : 1)Screw the legs directly into the desk?

2)Screw the legs into the support beams that are approx 20-30cm in from each end(that stops me putting draws underneath)

3)Glue/screw a extra support beam to the very ends of the desk, (the beam would be wider than the legs) to give me 2inch of wood to attach the legs too.

4) Other

Any advice would be much appreciated.

Answer 1

There are two sets of concerns you must address in designing the base for your desk.

First, it is my understanding that you have three leg locations for the top, one each at the ends of the "L" and one at the corner intersection. In that case, your span between legs is as much as 70. The wood appears to be pine in which case the sag that will occur appears to be within an acceptable limit, but use the Sagulator to confirm this. When the loads are too great it is necessary to add vertical aprons either at the edges or underneath the shelf/desktop.

Second, the desktop is made of solid wood pieces and will expand and contract width-wise (but not lengthwise) during the seasons while the steel leg base will not. As the wood expands pressure will be applied to the screws holding the top to the leg plates. If the screw holes in the steel plate are enlarged they should be able to accommodate the movement between the top and base. The amount of difference can be calculated as well. Here is one such site that explains the details of how to determine the amount of movement you might face.